Even in case of errors, as long as create fleet returns an instance,
attempt to use it.
In some cases AWS returns `InsufficientInstanceCapacity` but still
creates an instance:
```
msg="Won't retry CreateFleet with OnDemand instance, retry: false, errors: InsufficientInstanceCapacity: There is no Spot capacity available that matches your request.; Already launched instance ([i-...]), aborting create fleet"
msg="doCreateFleetRetry: returning retry: false, msg: [InsufficientInstanceCapacity: There is no Spot capacity available that matches your request. Already launched instance ([i-...]), aborting create fleet]"
msg="doCreateFleetRetry: cancelling retry, instance already exists: [i-...]"
msg="doCreateFleetRetry: setting retry to true"
msg="Checking to retry fleet create on error InsufficientInstanceCapacity (msg: There is no Spot capacity available that matches your request.)"
```
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